Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

278
FXUS63 KLOT 301948
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
248 PM CDT Thu Apr 30 2026

.KEY MESSAGES...

- Generally cool pattern to persist through next week
  with occasional chances for scattered showers.

- Patchy frost possible in northwest IL tonight, better coverage
  of frost Friday night into Saturday morning inland of Lake
  Michigan.

&&

.DISCUSSION...
Issued at 248 PM CDT Thu Apr 30 2026

A broad upper low continues to swirl above the Great Lakes and
adjacent Ontario with several shortwave disturbances noted
pivoting around the low. One of these shortwaves is currently
drifting across eastern IA and stating to move into northern IL
along with its baggy surface low. Associated with these features
is some light rain showers and sprinkles which will continue to
spread across northern IL and eventually into northwest IN
through the rest of the afternoon and evening. While this
initial wave of showers is expected to exit by midnight, another
shortwave (currently in the Dakotas) will pivot into the area
overnight and may bring with it another chance (20-30%) for
showers. Depending on how quickly this second round of showers
exits and clouds scatter out there could be just enough time for
temperatures to cool and lead to some patchy frost development.
The greatest potential for frost at this point is in northwest
IL, but if clouds clear faster that potential could ooze east.
Given the lower confidence on frost coverage have opted to hold
off on a Frost Advisory for now.

Friday will feature similar conditions to today with highs once
again in the mid-50s inland and in the upper 40s near the lake.
Though, cloud cover will be a bit more expansive as yet another
shortwave will be diving through the area. While mostly dry
conditions are expected for most, there is a non-zero chance
(15- 20%) for some isolated showers Friday afternoon. As the
shortwave disturbance exits Friday evening, skies should quickly
clear as a weak surface high moves overhead allowing
temperatures to dip into the lower to mid-30s. The combination
of clearing skies and light winds will make for favorable
conditions for widespread frost development Friday night into
Saturday morning. Should these trends continue we may need a
Frost Advisory for Friday night but will handle that with
tomorrows forecast package if needed. Regardless, anyone with
sensitive plants should take precautions to protect them.

The weak surface high and modest height rises are expected to
persist through Saturday which will give us a dry start to the
weekend. However, the continued northwest winds will keep highs
only in the mid to upper 50s inland and in the upper 40s to
lower 50s near the lake. With the ridging overhead it seems
skies should favor a mostly to partly sunny condition which may
once again lead to some frost development Saturday night into
Sunday especially in northwest IN.

Heading into Sunday, the continued troughing over the Great
Lakes is forecast to deepen as a more amplified shortwave trough
ejects out of Canada into the region. At the same time, another
trough/upper low is forecast to develop and be oozing inland
across southern CA and the southwest. These features will help
to generate stout southwesterly flow across northern IL and
northwest IN on Sunday which will lead to a slight warming trend
with highs in the mid to upper 60s forecast areawide. With the
warmer temperatures will also come the chances for showers and
possibly a few thunderstorms, but latest forecast trends do have
showers/storms holding off until Sunday evening when the
aforementioned Canadian trough arrives. If this trend continues
then Sunday may too be another dry day for us, however, if the
trough speeds up then we could see rain as early as Sunday
afternoon. Outside of the rain potential, winds on Sunday will
be breezy with gusts likely around 30-35 mph.

The better chances for rain from this system is expected to
occur on Monday when the Canadian trough pushes a cold front
through the region. Depending on when the front arrives, there
is a chance that temperatures on Monday could be the warmest of
the week with highs currently forecast to be in the 70s. Though
if the front comes through earlier then highs may be closer to
what we see on Sunday. Regardless, showers and thunderstorms are
expected to develop along the front and move through the area
into Monday night. While forecast soundings do show some decent
deep layer shear (around 35- 40 kts) moisture looks to be a
limiting factor which should keep the threat for any severe
weather low.

The cold front is forecast to shift south of the area on
Tuesday which should return the cooler temperatures to the
region as broad troughing remains over the Great Lakes. Thus,
highs in the 50s (locally cooler near Lake Michigan) should be
expected for the middle and later half of next week.
Additionally, periodic shortwave disturbances will continue to
dive through the broader trough and result in occasional chances
for showers especially towards the later half of next week.

Yack

&&

.AVIATION /18Z TAFS THROUGH 00Z SATURDAY/...
Issued at 1221 PM CDT Thu Apr 30 2026

Key Messages:

- Easterly wind shift at the main Chicago terminals ongoing
  with lake breeze boundary.

- A few scattered showers and locally lower CIGs mid to late
  this afternoon into this evening.

- Northerly winds turn northeasterly again across northeastern
  IL and northwest IN Friday afternoon.

A lake breeze boundary is currently moving right across ORD and
MDW, resulting in an easterly wind shift. In its wake, winds
will remain easterly the remainder of the day. Thereafter, winds
will ease through the evening, then turn back to the north-
northwest overnight into Friday morning before another lake
breeze shifts the winds back northeasterly at the Chicago
terminals Friday afternoon.

Otherwise, expect lower VFR CIGs this afternoon, along with some
scattered showers. The best shower timing will be from mid to
late afternoon into this evening.


KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

Visit us at weather.gov/chicago